1. Field of the Invention
This invention relates to a foil-roll electronic part and a process of producing the same, and more particularly to a foil-roll electronic part formed by rolling in a belt-shaped conductive foil or foils and a process of producing the same.
2. Description of the Prior Art
The inventor of the present invention has proposed a foil-roll electronic part wherein one or a plurality of belt-shaped conductive foils made of aluminum or copper are rolled on a magnetic or non-magnetic spool, or rolled on no core through insulating films of a high dielectric constant such as Mylar and polyethylene. This electronic part has an inductance wherein a stray capacitance is distributed over the total length of the belt-shaped conductor or conductors which has been rolled in or between the respective belt-shaped conductive foils. Owing to this characteristics, this electronic part can be used in the various fields as LC composite parts including a coil, a noise filter and a transformer.
This foil-roll electronic part utilizes a belt-shaped conductive foil or foils. Owing to this, an electric current of a relatively high value can be passed therethrough, a skin effect to a high frequency signal is minimal, the electronic part is compact in size, and yet, a high inductance and capacitance can be obtained, and the workability is satisfactory. Due to the above-described reasons, this foil-roll electronic part has a possibility of being widely used for the various applications, and particularly, it is ascertained by the inventor that, in the noise filter, an outstanding attenuation characteristics can be obtained.
Various noise filters using the belt-shaped conductive foil or foils as described above have been proposed by the inventor of the present invention.
As shown in FIG. 11(A) for example, two insulating films 10a and 10b which are formed of Mylar tapes and two of belt-shaped conductive foils 12a and 12b which are formed of aluminum foils are alternately superposed on each other and rolled into a tubular shape. At this time, leads 14a and 14c are connected by electric welding or the like to a roll starting portion and a roll terminating portion of one 12a of the belt-shaped conductive foils, which is used as a conductor for passing electricity. Furthermore, a lead 14b for grounding is connected by the same method as above to one end portion, preferably a roll starting portion of the other 12b of the belt-shaped conductive foils, which is used for a grounding conductor.
In the noise filter formed as described above, an inductance is formed between the leads 14a and 14c of the belt-shaped conductive foil 12a for passing the electricity, and yet, a capacitance is formed in the manner of a distributed constant between the belt-shaped conductive foil 12c for grounding and the belt-shaped conductive foil 12a for passing the electricity over the total length of the conductor 12a. FIG. 11(B) shows an equivalent circuit diagram of the noise filter thus formed.
Accordingly, when the lead 14b for grounding is grounded and the leads 14a and 14c of the belt-shaped conductive foil 12a are used as input and output terminals, respectively, noise filter having outstanding attenuation characteristics over a wide frequency band can be obtained.
Now, in the noise filter of the type described, it is required that the three leads 14a, 14b and 14c are arranged on a straight line at regular intervals as shown in FIG. 12(A).
If these leads 14a, 14b and 14c are arranged irregularly, then, particularly, the uniform attenuation characteristics and outstanding electric characteristics as in the noise filter cannot be obtained.
Further, these leads 14a, 14b and 14c should be arranged on the straight line at regular intervals, and yet, the lead arrangement should meet a hole pitch of a printed circuit board for being actually mounted thereon.
If this lead arrangement does not meet the hole pitch of the printed circuit board, then, the respective leads 14a, 14b and 14c cannot be inserted into the holes of the printed circuit board to mount the noise filter.
Normally, the foil-roll electronic part of the type described can be manufactured by use of a device analogous to a device for producing a paper capacitor.
However, if the above-described device is used, then, due to the values of the rollings being tightened in the condition of loosely rolled-up rollings at the time of roll-up, the arrangement of the three leads 14a, 14b and 14c is not definite and the respective leads tend to be shifted from one another as shown in FIGS. 12(B) and 12(C). Because of this, it has been extremely difficult to roll up such that the respective leads are regularly arranged at all times.
Moreover, such problems have been presented that, after the roll-up, the irregularly arranged leads 14a, 14b and 14c should be corrected to have a regular pitch, whereby the productivity is low and the production thereof is not suitable for bulk production.